The purpose of this project is to study the release of histamine from blood basophils and mast cells as one of the immunological mechanisms implicated in inflammation. Histamine-releasing agents studied included IgE antibody, formyl methionine-containing peptides and a complement factor (C5A) derived from human serum. The influence of anions and cations on the mechanisms of histamine release was studied. Although antigen-induced release requires only Ca ions, certain other ions were found which enhanced or inhibited the reaction. The desensitization of human basophils by environmental antigens was characterized as to the requirements for antigen dose, temperature and time. The release of inflammatory mediators from cultured mastocytoma cells is being compared with the mechanisms of release from basophils and mast cells collected from humans and laboratory animals. The research is being expanded to determine the role of IgE-mediated mechanisms in aphthous ulcers.